John Thorup touched on some applications where no-clean fluxes could be a bad idea. I'm looking for some more detailed info. (papers, references, texts, comparative test results, links, anything) that I can gain a little insight with. Our management is once again licking their chops at the idea of eliminating the wash process, and I'm sure that design is going to request some pretty beefy motivation before they agree to try and qualify product built to that spec.

Ahhhh, Dave, I'm glad I can still count on you for some real cutting edge info. yuck, yuck.

Believe me, there's a lot more information available on how to resolve no-clean issues than there is on how to keep this stupid board wash/DI/Stencil wash/evaporator system from puking DI all over the floor. If I EVER get my hands on the guy I inherited this process from.......

I cannot give references to papers, etc, but I can tell you from experience that High Impedance circuits and High Power RF circuits are not something to try no-clean on. For an aerospace customer, I had a circuit that any residue left between two pads on an IC would cause cross-talk. We even had to conformal coat between the leads using a syringe. Another customer had high power RF boards that the slightest residue would cause electrical interference or shorting. Maybe some folks in those arenas could help with facts or test results. I think it really depends on the product and design, and getting involved with the design folks and doing some experimentation in preproduction would be a big help.

At my last place of employment, that was the big reason why nobody (especially the Design Engineers) bought into a no-clean process - interference with high-impedance circuits.

One guy was so paranoid about flux residues remaining on the board, that one Design Engineer would make it his morning ritual to do a "straw test." What he would do was randomly sample a few boards after the in-line D.I. washer, blow his breath on the board with a straw to generate moisture on the high impedance area, and then test the voltage on a capacitor....if the voltage didn't fall within certain spec, he would make us run them through the washer again.

It realy depends on what no-clean you use, I had on that would get under IC's and not get fully activated it was fine here in the states but when it was shipped over seas the salt air and humidity gave us fits, another we used didnt have that problem but left a white residue that was hard to remove and if you dry brushed it whould take your breath away and if you tried to wash it it took high levels of saponifier 17% to remove it, I have found one that will clean easily and won't choke you. as for no washing we end up washing 50% + of are so called no-clean boards just for looks and probibly 10% for funtionality.